Nan Wang

Introduction: Coarse woody debris (CWD) plays a vital role in forest ecosystems, serving as a reservoir for carbon sequestration. While global climate change is expected to exacerbate forest disturbances and lead to a significant accumulation of CWD, the effect of CWD decomposition on the composition, diversity and functional traits of soil fungal communities remains unclear, especially for subtropical forests with high tree species diversity.Methods: Here, we conducted a 6-year in situ field experiment (2018–2024) in a subtropical evergreen broad-leaved forest in southern China. We used high-throughput sequencing and qPCR to examine how decomposition of three dominant tree species (conifer, broadleaved, and woody monocot moso bamboo) influences soil fungal composition, and applied the FUNGuild tool to infer fungal trophic modes and functional groups from sequencing data. We found that 6 years of CWD decomposition significantly increased soil organic carbon (SOC), dissolved organic carbon (DOC), and microbial biomass carbon (MBC) while reducing soil pH. Bamboo CWD showed the highest SOC and MBC accumulation.Results: High-throughput sequencing of the ITS1 region indicated a statistically significant increase in α-diversity and a marked differentiation in β-diversity of fungal communities following decomposition. Taxonomic analysis identified Ascomycota and Basidiomycota as the dominant fungal phyla. CWD decomposition was associated with observable differences in taxonomic composition, specifically an increase in the Basidiomycota-to-Ascomycota ratio. Key gener as such as Geminibasidium, Trichoderma, and Trechispora exhibited species-specific responses to both CWD decomposition and tree species identity. Functional analysis via FUNGuild revealed an increased relative abundance of taxa predicted to be saprotrophic, alongside a decreased relative abundance of taxa inferred to be symbiotrophic. Soil pH and SOC emerged as the primary factors influencing fungal community structure.Discussion: These findings highlight the critical role of CWD in shaping soil fungal communities and their inferred functional traits, underscore the influence of tree species identity on fungal assembly, and provide insights into stable carbon sequestration stability in subtropical forests.

Soil nematode communities play an important role in ecosystem material cycling and energy flow. In this study, soil samples were collected from three rotation systems in southern Ningxia mountainous region, including alfalfa continuous cropping (A-A), alfalfa-corn rotation (A-C), alfalfa-potato rotation (A-P). Soil physicochemical properties, nematode community composition and their metabolic footprints were measured. Compared with the A-A plot, the concentrations of soil organic carbon (SOC) and total nitrogen (TN) were significantly increased by 4.6% and 7.4% for SOC, 4.0% and 5.2% for TN in the A-C and A-P plots, respectively. Soil microbial biomass carbon and nitrogen were significantly higher in the A-C and A-P plots when compared with the A-A plot. The total abundance of soil nematodes in the A-C and A-P plots was higher by 49.5% and 93.7% than that in the A-A plot, respectively, with the dominant trophic group being changed to omnivores-predators from plant parasite. Compared to the A-A plot, the plant parasite index (PPI) was decreased significantly in the A-C and A-P plots, indicating that the harm of plant-parasites was reduced in soil food web. The nematode channel ratio (NCR) in the A-C and A-P plots were higher than that in the A-A plot, indicating that the role of bacterial decomposition was enhanced in soil organic matter decomposition. The maturity index (MI), the total nematode metabolic footprint, enrichment footprint, structure footprint in the A-C and A-P plots were all significantly higher than those in the A-A plot, suggesting that the structure and function of soil food web were more mature and stable, and the productivity and metabolic activity of nematodes were significantly enhanced. In general, the alfalfa-crop rotations improved soil nutrient status and reduced the disturbance degree of soil food web. Furthermore, soil ecosystem developed in the stable and healthy direction, which would be beneficial to the sustainable development of agriculture.

Acid rain has been regarded as a global environmental concern due to its negative effects on global ecosystems. In this study, we investigated the effects of simulated acid rain (SAR) on soil respiration rate and soil bacterial diversity in a Moso bamboo ( phyllostachyspubescens ) forest in subtropical China. Experimental results showed a similar seasonal pattern of soil respiration rates underdifferent SAR treatments. Seasonal mean soil respiration rates for CK (control, deionized water, pH 6.7), T1 (pH 5.6), T2 (pH 4.0) and T3 (pH 2.5) treatments were 3.44, 4.80, 4.35 and 4.51 μ mol m ⁻² s ⁻¹ , respectively. One-way analysis of variance indicated that the SAR exposure had no significant effect on soil respiration (p>0.1) and soil microbial biomass (p>0.1). Soil bacterial community diversity was calculated as the Shannon-Wiener diversity index and the results showed that only T3 treatment had significant effects on soil bacterial diversity. The DGGE analysis results revealed that T1 and CK soils had closer association and were related to the T2 soil, while T3 soil was distinctly different from the other treatments. This work highlights that the effects of SAR are important to consider in assessing the soil respiration rate, particularly under the scenario of increasing acid rain pollution.